What are the various uses of elemtype?

Elemtype is a template metaprogramming tool used in C++ to retrieve the type of elements in a container. Its main purpose includes:

1. Type inference: When writing generic code, you can use `elemtype` to infer the type of elements in a container, making the code more generic and flexible.
2. Type checking: elemtype can be used to check if the type of elements in a container meets certain requirements, such as being a specific base class or adhering to a specific interface.
3. Type conversion: elemtype can be used to convert elements in a container to other types to meet specific needs.
4. Metaprogramming: You can use elemtype for compile-time computation, for example in template metaprogramming to perform specific operations or generate specific code based on the type of elements in a container.

In conclusion, the purpose of elemtype is to easily obtain the type of elements in a container when writing generic code, and perform related operations at compile time.